Modern turboprop and turbofan powered aircraft carry a gas turbine engine known as an auxiliary power unit (APU) in addition to the main propulsion engines. The APU serves two main functions: to provide power to aircraft systems when the main engines are not running, and to enable starting the main engines without need for external power. In many business class aircraft and in aircraft used by smaller regional airlines, the APU is mounted in the tail end of the fuselage generally known as the tailcone. Typically, the engine supplier and tailcone casing supplier coordinate with the aircraft manufacturer in the installation of the APU at the manufacturer's facility. The APU is custom fit and mounted to the aircraft, and all accessories such as electrical, pneumatic, and fuel, are routed to the APU and connected. The tailcone casing supplier then fits and installs the casing, usually including an openable or removable panel for access to portions of the APU.
A problem with this kind of APU installation is the large amount of the time and expense involved in completing an installation. The mounting of the APU and routing and connection of accessories requires substantial effort by skilled technicians and engineers from the aircraft manufacturer and APU supplier. Fitting and attaching the casing requires technical support from the tailcone casing supplier as well. A complete installation can take days or even weeks at the aircraft manufacturers facility resulting in substantial cost and inconvenience.
Another problem results from inaccessibility of the APU once the casing is in place. Typically the casing comprises two large panels that are attached to one another and to the aircraft using numerous screws. The casing includes at least one small openable door for providing access to routinely monitored items such as the oil sight glass. However, for anything beyond the routine day to day maintenance it becomes necessary to remove at least one of the large casing panels. Removal of just the screws holding the panels together can take thirty minutes or longer. The time spent on removing and reinstalling the tailcone casing can become particularly inconvenient and costly when it results in unplanned delay to scheduled flights.
Accordingly, a need exists for a system that substantially reduces the time and labor required to install and test an APU and tailcone casing onto an aircraft. Another need exists for a tailcone casing that provides quick access to the entire APU mounted therein.